In recent years, in a system such as a computer system, a liquid crystal display apparatus, a plasma display apparatus, an image display apparatus which uses organic EL (Electroluminescence) devices and so forth have been developed, and development of image display apparatus of a reduced weight and thickness have been and are proceeding remarkably. As one of image display apparatus of a reduced weight and thickness, also a display apparatus whose display screen is formed by arranging a plurality of a light emitting diodes used as light emitting devices has been proposed. In an image display apparatus in which a light emitting diode is used, a plurality of light emitting diodes which individually emit blue light, green light and red light are formed on a semiconductor substrate and then arranged in a matrix on a displaying face. Thereafter, formation of wiring lines for driving the light emitting diodes and so forth are performed. In order to arrange the devices formed on the semiconductor substrate at predetermined positions of the display apparatus, transfer of the light emitting diode devices is performed. In order to perform the transfer, a method of disposing devices at required positions using vacuum absorption is widely used. Further, as a technique for forming wiring lines, a wire bonding technique or the like is used.
Light emitting diodes are fabricated using a semiconductor material of a gallium arsenide (GaAs) type, gallium/indium phosphorus (GaInP) type or gallium nitride (GaN) type which are expensive materials. Therefore, it is desirable to make the size of devices smaller in order to decrease the fabrication cost per one device. However, it is difficult to vacuum absorb fine light emitting diodes to arrange the devices at positions corresponding to a display screen and then form required wiring lines. Further, also it is difficult to enhance the positioning accuracy upon the arrangement of the devices. Therefore, also a method has been proposed wherein fine light emitting diode devices formed in an equally spaced relationship from each other on a substrate are selectively exfoliated and transferred to a different substrate. The method is disclosed, for example, in Japanese Patent Laid-Open No. 2003-77940 (hereinafter referred to as Patent Document 1).
In the device transfer method disclosed in Patent Document 1, in order to selectively exfoliate fine light emitting diode devices from a substrate, a laser ablation technique is used wherein a laser beam having a small diameter is irradiated those devices which are to be exfoliated so that chemical variation or mechanical variation on an interface between the substrate and the devices is caused to weaken the bond between the devices and the substrate. In the laser ablation technique, in order to selectively irradiate the laser beam on fine devices formed in a crowded relationship on a semiconductor substrate, a laser beam having a reduced diameter must be irradiated on the devices. Therefore, a method is used wherein the laser beam to be irradiated is condensed by an optical member such as a lens.